Explanation: Because of mass production of materials came into play the Europe started with new weapon innovations. Because of this they were actually curious to know what these weapons could do. Not only that but the idea of Serbian nationalism was promoted in support for a more unified Slavic state. This lead to Gavrilo Princip a member of the black hand a Serbian nationalist group to assassinate Arch Duke Franz Ferdinand and his wife Sofie. This lead to Austrian aggression against the Serbs but the Serbs were backed by the Russians because both countries were of Persian roots and Russia essentially big bothered Serbia. This inevitably pulled in all the countries alliances into a conflict with each other. The US only got involved when a message known as the Zimmerman note was intercepted and was intended to turn Mexico against the US.